The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. In the course of integrated circuit evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased.
The ever-shrinking geometry size brings challenges to semiconductor fabrication. For example, as the device sizes become smaller, variations in device density or size across different parts of the semiconductor device may cause loading problems. The loading problems may lead to undesirably high resistance, for example.
Therefore, while existing semiconductor fabrication technologies have been generally adequate for their intended purposes, they have not been entirely satisfactory in every aspect.